This invention relates to operating means for a latch, for example, a door latch.
A door latch set as conventionally used comprises an insert fitted into the free edge of the door between its front and back surfaces having a bolt which in its extended position protrudes beyond the edge of the door into a recess in the door frame and in its retracted position is wholly within the door to allow the door to be opened. The bolt is conventionally moved between its retracted and extended positions by rotation of an element of the latch set by rotation of a square section spindle extending through the door. Rotation of the spindle is usually effected by action of a door handle or knob on the spindle. The bolt will usually be biased to its extended position.
The bolt may be lockable in the extended or retracted position by a mechanism which prevents rotation of the handle or knob.
In addition to the type of latch set which uses a rotating handle or knob there is a further type of latch operating means which uses a linear rather than rotary action to move the latch bolt between its retracted and extended positions. Several latch operating means utilising a linear movement towards or away from the door to retract or extend the latch bolt appear in Swedish Patent No. 348700, UK Patent No. 2070128 and UK Patent Applications Nos. 8602700, 8602701 and 8602702.
The present invention is concerned with improvements to latch operating sets comprising first and second latch operating means to be located respectively on opposite sides of a door or the like, each latch operating means being connected through a latch operating member to a latch operating spindle such that operation of the latch operating means causes rotation of the appropriate latch operating member and thereby of the spindle. The spindle may be of the square type such as is defined in British Standard BS No. 5872 (1980) for latching sets, or indeed of any other section of varying radius to provide the necessary camming action. This type of latch operating set will be referred to in this specification as a latch set "of the type specified".